1. Field of the Invention
The present invention relates to a motion control apparatus and more particularly to a six axis motion control apparatus for non-contact scanning of a surface of an object.
2. Description of the Prior Art
Three dimensional scanning is an important component associated with the manufacturing process. Optical three dimensional scanning is accurate and a cost-effective alternative delivering more dimensional information to aid in quality control and process optimization. The ability to provide the designed geometry to meet the designer's intent and achieve the engineering dimensional requirement to deliver the intended fit and functionality is an ongoing challenge during the manufacturing process. Optical three dimensional scanning is based on the principle of triangulation. A sensor unit projects different fringe patterns onto an object to be measured. These patterns may then be recorded by two cameras. Based on the optical image equations, a computer may automatically calculate the three dimensional coordinates. In order to digitally render the object completely, several individual measurements from various views are required. After scanning is completed, a software program may be used to calculate a complete high-resolution polygon mesh of the object surface, creating small triangles in curved and large triangles in flatter areas without diminishing the mesh's accuracy.
Traditionally, in a first article inspection, an inspection plan is created based on the CAD data. This plan defines the features to be measured and their corresponding tolerances. For complex parts, several hundred features may need to be measured. The task of measuring these features can be time-consuming with a tactile measuring device. Even after the measuring is complete and the report is generated it is still difficult to identify the problematic areas and determine corrective action due to the lack of full part information. A new procedure is made possible with the use of a white light volumetric scanner which may be used to create and complete a test plan. The first article of inspection process is expedited via the use of full-field scanning and using full color plot images.
In order to measure, assess and document the inspection of numerous identical parts during sampling checks, production ramp-up and for production control, two additional components are required: a handling device for the sensor or the component and a macro recorder in the software for the automation of measurements, data evaluation, protocol generation and output. The ability to speed the production of a broad range of manufactured parts (from engines to medical devices) is desired.
To obtain a three dimensional scan of a surface of an object, the scanner may be held by an individual. The individual may then begin scanning the surface of the object from a variety of different perspectives and angles to achieve a comprehensive scan of the object. However, scanning and measuring an object by having an operator holding the scanner is tedious, time consuming, and not conducive to repetition. To overcome some of the issues associated with using the scanner, the scanner may be placed on a tripod. The tripod configuration still requires manual movement of the scanner by an operator. But the tripod may improve the operator's ability to repeat certain positions with little discrepancy from past measurements. The problem with using a tripod is the limits of various perspectives that are achieved when scanning an object. Typically, for each new scan, the scanner must be repositioned. To address these problems manufacturers may use various devices that enable some automatic component repositioning. Unfortunately, the scan of the object or work piece with these devices may produce undesired shadows, making completely automated scanning less feasible.
An improved method of obtaining a three dimensional scan involves the use of a coordinate measuring machine (CMM). The CMM may be manually controlled by an operator or computer controlled. A typical CMM may be composed of three different axes that are orthogonal to each other. Each axis has a very accurate scaling system that indicates the precise location of that axis. Using a CMM device is more accurate and results in faster scanning times than a three dimensional scan using a handheld scanner. CMM devices may be combined with white light volumetric scanner's that provide laser scanning. Laser scanning uses laser beams that are projected against the surface of the object to be scanned. Thousands of points are taken and used to validate size and position of the object and to create a three dimensional image of the object. Data is generated and transferred to CAD software to create a three dimensional model of the object. However, even with the technological advances associated with CMM devices, collecting measurement data and manual inspection techniques are very time consuming.
Non-contact scanning systems known in the art may be used to reduce the time required for a three dimensional scan and measurement of an object. As understood, one such non-contact scanning system provides a more comprehensive scan than a three dimensional scan using conventional CMM devices, tripods, or manual operation. The non-contact scanning system provides automation that allows for repeat scanning of similar objects for accuracy. Unfortunately, these scanners may be limited with respect to some of its movements. This may result in less comprehensive scans and measurements of the object with respect to certain perspectives.
Accordingly, there exists a need in the art for a motion control apparatus enabling non-contact three dimensional scanning which addresses one or more of the deficiencies identified above, known in the art or discussed below.